MRI Assessment of Degeneration of Multifidus and Erector Spinae Muscles in Patients With Chronic Low Back Pain

Abstract Background: The aim of this study was to investigate the degeneration of lumbar musculus multifidus (L.MF) and lumbar musculus erector spinae (L.ES) muscles in healthy individuals and patients with mechanical low back pain and lumbar discopathy without root compression (radiculopathy), and to examine the relationship between low back pain by comparing the results according to gender, pain and lumbar segments between the groups. Methods: The study included 30 healthy individuals (Group 1), 30 patients with mechanical low back pain (Group 2) and 30 patients with lumbar discopathy without root compression (radiculopathy) (Group 3). Pain severity was evaluated using a Visual Analogue Scale (VAS). Right and left L.MF and L.ES cross-sectional areas (CSA), total cross-sectional areas (TCSA =L.MF+L.ES), fat infiltrations, and asymmetries between the right and left sides were evaluated. L.MF and L.ES muscles CSA and TCSA, fat infiltrations, asymmetries between the right and left sides were evaluated in the patients at the L3-S1 level, in axial Magnetic Resonance Imaging. Results: The mean value of the CSA differed between the groups only in the right L.MF and in the healthy group (p=0.011). No statistically significant difference was observed between the TCSA values of the groups, but a significant difference was found between the groups in terms of fat infiltration in right and left L.MF and left L.ES (p=0.011, p=0.001, p=0.027, respectively). When CSA and TCSA were examined according to gender within the group, the values were found to be significantly higher in males (p<0.001). The CSA and TCSA values ​​of L.MF and L.ES differed between segments (L3-L4, L4-L5, L5-S1) (p<0.001). There was no asymmetry between the right/left CSA and TCSA of the groups. Fat infiltration differed according to gender (p=0.001) and segments (p<0.001). Conclusion: Fat infiltration in the lumbar multifidus muscle was associated with mechanical low back pain and lumbar discopathy. The fact that there was no difference between the cross-sectional area and the total cross-sectional area between the groups indicates the need to measure the FCSA or muscle atrophy due to fat infiltration in the evaluation of muscle mass, rather than CSA and TCSA.